In one form of a fluid flow control valve, a flow control element or valve member is movably positioned in a valve chamber between first and second valve positions for selectively fluidically coupling valve ports. The flow control element may be directly actuated by a solenoid operated plunger operatively associated with the flow control element. The solenoid coil controllably positions the plunger to move the flow control element to an actuated position.
Typically, the valve chamber is provided by a valve housing of a magnetic material capable of withstanding high fluid pressure. The plunger is slidably received in a sleeve brazed between the valve housing and a tube stop. To bias the plunger to a normal, or unactuated position, the plunger typically includes a counter bore at either end receiving a spring biasing the plunger in a suitable direction. This type of assembly requires increased manufacturing costs.
A typical application for a cartridge valve of the three way, two position type is in an automobile transmission for switching clutches and the like. Typically, the clutches are single acting cylinders operated at relatively low pressure on the order of five to six hundred psi, with one thousand psi being a maximum. As a plurality of valves may be necessary in such applications, economies in manufacturing are desirable to provide cost effective solutions to satisfy control requirements.
An additional problem in transmission applications results from the use of cartridge valves having magnetic housings. In an automotive transmission box, metallic chips and the like may result from gear wearout. Energization of the solenoid in proximity to a magnetic valve housing attracts the chips causing valve sticking problems. This problem can be minimized using filters or screens in valve manifolds or the like. Here, again, additional parts and expense results.
The present invention overcomes one or more of the problems discussed above.